i think its a trojan, considering the effects. most trojans and some script virus hides the .exe files, like what happened in my system a few days ago. i cant execute run, the taskbar (ctrl,alt,del) and system restore it also disables most of the administrator priviledges.
using the repair installation of avast and uninstalling it again i think will do the trick. but if some of your o.s services are not fully operational i think it might be the result of moving the infected file (quarantine) instead of using repair especially if the infected file is the .exe or some missing dll's.
if you tried online scanners and they can't do the job before its done I think your system is infected by a script virus that prevents any program from accesing the file system (deadlock= prevents a file from being accessed if its currently being used). if you can access your taskmanager try searching for a script that's running or go to msconfig and go to startup and see if there are any startup programs that looks malicious (different or the path of the file doesnt make any sense usually composed of ascii characters thats unreadable) just disable it restart and see what happens. if you have updated you avast virus database and can't remedy your system you might have to wait for a while for another update to fixed the virus. sorry
we have to understand that there is no such thing as a perfect antivirus software thats the reason why software evolves it has to constantly update the engine or its database to be effective) and dont expect a lot from free softwares, i do believe most of the best ones in life doesnt comes for free! hehehe
dont get me wrong im also using home... pro is expensive for most of us...I think.
